Rubber article and method of making the same



Jan, 28, 1936. 1.. M. ROSENTHAL RUBBER ARTICLE AND METHOD OF MAKING THESAME Filed July 1, 1933 ATTORNEYS.

Patented Jan. 28, 1936 UNITED STATES PATENT OFFICE RUBBER. ARTICLE ANDMETHOD OF MAKING THE SAllIE Application July 1, 1933, Serial No. 678,571

11 Claims.

My invention relates to a new and improved rubber article, and a new andimproved method of making the same.

One of the objects of my invention is to pro- 5 vide a new and improvedrubber article of hollow shape.

The invention applies generally to all rubber articles, such as rubberballs, hollow rubber dolls, or other toys, hot-water bags, the innertubes of tires, and it generally applies to all articles which haveheretofore been made by joining together two or more sheets of sheetrubber, or which have been molded from a single sheet of rubber.

In certain aspects of the invention, the same is not limited to a hollowrubber article, as the invention generally applies to all articles whichhave heretofore been manufactured by joining two or more sheets of.sheet rubber, or by molding a single sheet of rubber.

Another object of my invention is to greatly reduce the cost ofmanufacture by reducing the cost of the molds, and by making itunnecessary to utilize liquid or gas pressure, during the vul- 5canization operation.

Another object of my invention is to provide a method whereby theinterior of a mold (which can be made in any desired number of sections)is lined with a suitable rubber compound in viscous form, and the rubberis then vulcanized by means of heat or the like.

Other objects of my invention will be set forth in the followingdescription and drawing which illustrate a preferred embodiment thereof,it be- 3 ing understood that the above general statement of the objectsof my invention is intended merely to generally explain the same and notto limit it in any manner.

Fig. 1 diagrammatically illustrates a mold section which is providedwith a lining of rubber cement.

Fig. 2 shows a pair of mold sections suitably assembled in order tovulcanize the rubber.

Fig. 3 is a partial view of a pair of assembled molds.

Figs. 4 and 5 illustrate modifications.

Heretofore, in making articles such as rubber balls, hollow rubber toys,inner tubes of automobile tires, etc., it has been the universalpractice to first make sheets of rubber by means of calenders or thelike, to then assemble the sheets of rubber by forming joints, either bymeans of cement or rubber solvent or by welding, and to then vulcanizethe assembled sheets in a mold while supplying a medium under suitablepressure within the interior of said mold, in order to firmly press therubber sheets against the inner surfaces of the mold members.

In some methods it has been customary to force hot water under pressureinto the interior of the mold and it also has been customary in othermethods to force steam into the interior of the mold.

According to a third method, a chemical contained in a capsule has beenplaced into the interior of the mold, so as to release gas underpressure when the heat of vulcanization was applied. These methods werecostly and uncertain.

According to my improved method, I first prepare the rubber compound inviscous or cement form. This is done by working up the rubber in asuitable mill with the added ingredients such as sulphur or othervulcanizing ingredient, and the various compounding ingredients whichare ordinarily added to the pure rubber stock. The accelerators,anti-oxidants, and other ingredients, are also thoroughly intermixedwith the rubber stock.

After the dry mixture has been thoroughly; made, the mixture is putgradually into a churn, which contains naphtha, or other suitablerubbersolvent, and the naphtha is worked into the dry mass until arubber cement has been made of suitable viscosity. The cement issufiiciently thick and viscous so that it will flow very slowly, and itis either applied by means of a brush or stick, or else it can be forcedthrough a nozzle, under suitable pressure. In order to distinguish fromthe use of unvulcanized sheet rubber, I state that I spread the rubbermaterial, since it is in spreadable form, it can be applied by the meanspreviously mentioned.

Referring to the annexed drawing, Fig. 1 H- lustrates a semi-sphericalmold A having a lip or flange B. The interior of the mold A and thecorresponding surface of the flange B is provided with an inner layer ofrubber R, and said inner layer is preferably of uniform thickness. Thisinner layer of rubber R is made by spreading the viscous rubber cementwhich has been previously described, upon the corresponding surfaces ofthe mold A and of the flange B.

In order to make an ordinary rubber ball, two such half-molds A can beused, or else the com-' plete spherical mold can be divided into anydesired number of sections such as six or eight or more.

In molding a large article the mold can be made of relatively fewsections. In molding a small article such as a rubber ball of smalldiameltl ter, the mold can be subdivided into a number of relativelylarge sections. That is, a greater curvature requires a larger number ofmold sections.

If a nozzle is used for distributing the rubber cement, this can haveany desired shape. If desired, the mouth or outlet of the nozzle cancorrespond in shape to the respective mold section, including the flangesection thereof. Likewise any suitable mechanical movement can'beutilized for producing a relative movement between the nozzle and themold section, in order to deposit a layer of rubber cement R of uniformthickness.

For example, in making the inner tube of a tire, the mold can be dividedinto two or more annular sections. The outlet or mouth of the nozzle cangenerally correspond in shape and size to each of these sections,including the flange section thereof, so as to provide a layer R ofuniform thickness. Likewise any excess thick- I ness of rubber cementcan be removed by hand or any suitable means.

When the mold sections have thus been lined. with a rubber cement, saidsections are assembled with their flange sections adjacent each other.This assembly is shown in Fig. 2, from which it can be seen that themold sections are held together, without squeezing out the lip or flangesections of rubber cement, as these lip or flange sections areused forforming the joint between the respective parts of the article. Ifdesired, some pressure can be applied to the mold sections when they areassembled so that.

the lip sections Ra of the rubber cement may be thinner than the body ofsaid rubber cement, when the mold sections are assembled in the mannershown in Fig. 2.

The lip sections of the rubber cement may be made as thin as is desired,and said lip sections can also be made thicker than the body of therubber cement, if this is desired; Since the rubber article isvulcanized while the rubber sections are unsupported by any interiorpressure, the

. joints between the rubber sections are irregular,

and the completed article can thus be distinguished from an articlewhich has been made by the use of ordinary sheet rubber, as for examplean article made according to U. S Patent No. 1,400,146 issued onDecember 13, 1921.

The'final article has superior strength because it is not necessary towork the rubber on the mixing mill in order to form sheet rubber.According to my invention the ingredients may be mixed together with theuse of a solvent which enlarges or swells the rubber. After the rubbermaterial has reached the desired consistency, said material is depositedin the form or mould and it is then vulcanized.

Likewise while I have referred to making the rubber article of uniformthickness, it is a great advantage of my method that added thickness canbe conveniently provided whenever desired,

' by merely depositing additional rubber cement at the interior of theassembled molds.

Said

Likewise said reinforcing members may be flush or substantially flushwith the outer surface of the rubber article, if desired. Likewise therubber article may be formed with one or more openings therein, as forexample in making a hot water bag.

Likewise any suitable metal member, such as the nipple of a hot waterbag, can be held within the mold, while the rubber cement is beingapplied, so that the vulcanized article will have the nipple already inposition.

Various other modifications can be utilized, depending upon the natureof the article .to be manufactured.

The assembledparts shown in'Fig. 2 are then placed in a suitablevulcanizing chamber which may be provided with steam in the usualmanner.

Likewise the vulcanization may be accomplished by means of dry heat, bymerely placing theassembled mold sections in a suitably heatedchamberwhich may be heated by a steam jacket or the like. V I

Before assembling-the molds in' the manner shownin Fig. 2, and beforeVulcanizing therubber, most of the solvent is allowed to evaporate.

This evaporation is very rapid and it is accom plished at ordinary roomtemperature. The choice of the solvent and the rapidity of theevaporation thereof may depend upon the size of the rubberarticlebecause if a large mold is to be lined with the rubber cement, it ispreferred that the solvent should not evaporate as rapidly as if a smallarticle is being made.

During the, vulcanization, the mold is not subjected to any excessivepressure, eitherinternal or external. It is not necessary to introduceany fluid under pressure (either liquid or gas), into Hence it is notnecessary to make expensive and strong molds, and the molds or moldsectionscan be quickly or easily stamped out of tin plate or duralumin.

I prefer to make the mold out of rust-proof material, or to provide saidmolds with a rust-' proof coating or plating. This facilitates theproduction of a colored rubber which has the desired true color, becausethe color of a rubber compound is affected if it comes into contact witha metallic oxide (produced by rusting), during the vulcanization.

According to my method, I can utilize absolutely dry heat for performingthe vulcanization, so that the rusting is minimized.

The completed rubber article is provided with a lip or lips, dependingupon the method of manufacture. Ordinarily the completed article has asingle lip, which corresponds to the lip or flange portions Ra ofthe'rubber cement. This lip is not objectionable in the manufacture ofhot water bags, rubber balls, etc. Where such lip is objectionable, itmay be removed by any suitable cuttingoperation, so as to provide asubstanti'ally smooth exterior for the completed rub-' ber article. Suchsmooth exterior is desirable in making the inner tubes of automobiletires although a small lip is not objectionable.

It will be noted that the rubber article is joined at a line in theinterior of the rubber article. Likewise additional rubber cement may bedeposited at the zones D and E, in order to reinforce the rubber articleat the joint thereof. Hence the lip or flange portions Ra can be made ofminimum width, because the completed article does not depend upon thelip for holding the parts thereof together.

If desired, the flange sections B can be corrugated or fluted, eitherlongitudinally or laterally (radially) so as to provide a stronger jointfor the completed article. Likewise the rubber cement may be ofdifferent grades, one kind having much more rubber than the other. Thehigher grade compound can be used for forming the exterior of thearticle, and the lower grade compound can be used for forming theinterior of the article.

As illustrating the flexibility of the method disclosed herein, it hasbeen proposed to make dolls having skeletons made of aluminum or othermetal and to cover such skeletons with a thick rubber skin, in order toproduce a light and hollow doll whose outer surface has a natural fleshcover, said outer surface being made of rubber.

According to myinvention, the skeleton can be assembled so as to providean inner form, the viscous and tacky rubber cement can be deposited uponthe inner surfaces of mold members, and

: the mold members can be placed around the form, so that the form ispartially-or wholly imbedded in the cement. The cement is then vul-,canized, the mold members are removed, and the cement forms a completevulcanized covering for the skeleton, so as to simulate any type ofrubber doll or toy or form of any kind.

This method can be used for forming a complete or partial jacket for abarrel or other article. This jacket remains vulcanized to the barrel orthe like, and forms an outer protective cushion.

If desired, the interior surface of the mold section or sections can bedusted or coated with an anti-adhesive compound, in order to prevent thevulcanized rubber from clinging to the mold section or sections. Howeverit is a great advantage of my invention to have the mold section orsections made of smooth and highly polished tin plate, or similarmaterial, so that it is not necessary to provide any anti-adhesivematerial.

The elimination of the anti-adhesive material .makes it possible toprovide the rubber article with maximum strength and in any desiredcolor, because the use of anti-adhesive material would affect thesurface color of the article.

If it is desired to manufacture a rubber article of concave form such asone-half of a doll body or a rubber dish or the like, I can use male andfemale mold members F and Fa of the usual type, the cement being appliedto the adjacent surfaces of the said mold members, or to the outersurface of member F.

Whenever I refer to an article made of rubber, it is to be understoodthat I include pure rubber and compounded rubber of every type.

While I have referred heretofore to the admixing of rubber with asolvent, in order to produce the rubber material in viscous form, I donot wish to be limited to this. For example, it is well known that latexcan be admixed with suitablev materials, or be suitably treated, so asto produce a viscous material. Such material can be defined as being.rubber material in viscous form, even though it may not contain asolvent for rubber. Whenever I refer to unvulcanized rubber in viscousform, I refer to rubber which is suficiently adhesive to cling to theinterior of the mold while the rubber is unvulcanized, and said rubberdoes not flow when it is deposited upon the interior surface of themold. The rubber may be designated as being self-adherent, because itdoes not require the use of gas pressure to hold it against the mold,during heat vulcanization.

Referring to Fig. 4, this illustrates the formation of an article, suchas a rubber ball, Without a lip. The mold sections A have internal lipsG, about which the layers of rubber cement D and E are deposited. Therubber article is thus formed with a circumferential depression (whichmay be very narrow and shallow) in its outer wall. The vulcanized layersD and E reinforce the joint.

While I have previously referred to the evaporation of naphtha or othersolvent for the rubber,

this evaporation need not be complete, and in actual practice suchevaporation is never complete prior to vulcanization. Enough naphthamust be retained so as to cause the unvulcanized rubber material toadhere to the inner surface of the mold. However, enough naphtha must beevaporated so as to prevent the generation of excessive vapor during theheat vulcanization. Since the mold sections are not clamped togetherwith any great force, the generation of such vapor would cause the seamor joint between the rubber sections to open, and this would be highlyundesirable.

The rubber compound which is used in practicing my invention may be of atype which produces a resilient rubber. may be so compounded as toproduce a hard rubber when the same is vulcanized, so that the inventioncan be used for making the parts of fountain pens, and other parts whichare now made of hard rubber.

While I have referred to the production of hollow rubber articles, theinvention also applies to the production of fiat or planar rubberarticles.

Since the unvulcanized rubber material tends to soften and to flow ifthe same is heated too high, I prefer to use as low a vulcanizationtemperature as is practical and to have the vulcanization period asshort as is practical.

In making an ordinary article out of viscous rubber cement or the like,which has a large percentage of pure rubber, I prefer that thevulcanization temperature should not exceed 220 F., it being noted thatthe sulphur does not begin to combine with the rubber until thetemperature exceeds about 175 or 180 F.

Indeed, in making a thin rubber article, such an article having athickness of about .04 inch, I can use a vulcanization temperature aslow as 185 F., and vulcanize the rubber for a period of thirty minutesor more, at said temperature. This period of treatment at thevulcanization temperature is longer than the usual treatment atvulcanization temperature. That is, in prior practice in using thickiron molds, the molds were slowly heated to a vulcanization temperaturewhich was more than 220 F., and the rubber was kept at the highesttemperature for ten minutes or less.

After the vulcanization has been completed, the completed article,together with the molds,

Likewise, the rubber of thin material such as tin plate of about No. 30

gauge (having a thickness of approximately .0125 inch).

If desired, a rubber garment can be made by using suitable molds whichcorrespond to the parts of a garment.

By assembling these molds, the unvulcanized viscous rubber materialassumes the contour of a garment. When the rubber material has beenvulcanized, it can be'removed from the molds, thus producing a completegarment without the necessity of cementing or otherwise joining thevarious parts of the garment. the rubber compound can be applied byspraying.

An article made according to my method is completely formed fromunvulcanized rubber ma= terial which has been joined'so as to bevulcanized in situ. Hence the completed rubber article has a joint, suchas a flange or the like, which is superior in strength to an articlemade by cementing or pressing together, sheets of unvulcanized rubber.

Likewise the thickness of the lip or flange can be less than thethickness of the body of an article.

If the interior of a seam of ticle made according to my the improvedarinvention is examined, it can be seen that the seam is irregu lar,whereas the seam which is produced by connecting two sheets of sheetrubber is regular, and follows a definite plane.

The use of thin molds of high conductivity and of low thermal capacityis an important feature of the invention. This enables the viscousrubber material to be very quickly heated and vulcanized, if thetemperature of vulcanization is 212 F., and even less. If the solvent iscompletely evaporated from the cement during the initial stage of thevuieanization, it does not cling properly to the interior of the mold.By drying in air at ordinary room temperature of about 70 enough solventcan be driven off, while retaining the tackiness of the cement. Thevulcanizing heat then passes very quickly through the thin mold, thusbeginning the vulcanization of the rubber before the heat completelydrives oii the residual solvent. This causes the rubber material tocling to the mold, and to retain the desired shape, until thevulcanization is completed.

Whenever I refer to the deposition of rubber material, it is to beunderstood that I exclude the use of sheet rubber.

I have shown preferred embodiments of my invention, but it is clear thatnumerous changes and omissions could be made without departing from itsspirit;

Referring to Fig. 5, the principle illustrated therein can be appliedwith the use of a mold of any shape. For example, a figure correspondingto the upper part of the body of a human being can be covered with thecement, so as to form a cementcover'mg which corresponds to a coat, andwhich has arms and sleeves. Said coating of rubber cement may beinterrupted along a suitable line. Corresponding outer molds may beplaced over and in contact with the rubber cement, and the molds can beheated, to vulcanize the cement. The outer molds can then be removed,and the vulcanized rubber coat can be removed from the form.

consists in depositing upon the surface of a moid If desired,

member the unvulcanized rubber material intermixed with solvent and inviscous form, and then vulcanizing he rubber by heat, said rubbermaterial being permitted to retain sufficient solvent prior to completevulcanization to cause it to adhere to the mold member.

2. A method of forming a hollow rubber article which consists inspreading the unvulcanized rubber material in viscous and self-adherentform upon the surfaces of a plurality of mold sections which areprovided with lips, said unvulcanized rubber material being alsodeposited upon said lips, assembling said mold members so that theunvulcanized rubber material has'the conformation of the desired articleand the lip portions of said unvulcanized rubber material contact witheach other, and then vulcanizing said rubber material by heat while saidmold members are held in said relative position, the vulcanization beingcompleted before the rubber material has lost its adherence to the moldsections.

3. A method of forming a hollow rubber article which consists in,spreading the unvulcanized rubber material in viscous and self-adherentform upon the surfaces of a plurality of mold sections which areprovided with lips, said unvulcanized rubber material being alsodeposited upon said lips, assembling said mold members so that theunvulcanized rubber material has the conformation 5f-the desired articleand the lip portions 1 of said unvulcanized rubber material contact witheach other, then vulcanizing said rubber mate-' rial by heat while saidmold members are held in said relative position, and then trimming thevulcanized rubber lip which is thus formed, the r;.

vulcanization being completed before the rubber material has lost itsadherence to the mold sections.

4. A method of forming a hollow rubber article which consists inspreading unvulcanized rubber in viscous and self-adherent form upon thesurfaces of a plurality of mold sections while depositing said materialin greater thickness at the margins of said mold sections, assemblingthe mold sections so that the unvulcanized rubber material has theconfiguration of the desired article, and then vulcanizing the rubbermaterial by heat while the mold sections are held in said relativeposition, the vulcanization being completed before therubber materialhas lost its adherence to the mold sections.

5. A method of making a rubber article which consists in depositing uponthe interior surface of a mold. member, unvulcanized rubber material inviscous and self-adherent form and intermixed with a solvent for rubber,allowing the solvent to partly evaporate while retaining saidself-adherent state, and then vulcanizing the rubber material by heat.

6. A method of forming a hollow rubber article which consists indepositing unvulcanized rubber in viscous and self-adherent form andintermixed with a rubber-solvent upon the surfaces of a pluby heat whilethe mold sections are held in such relative position. I

7. A method of making a rubber article which consists in coating thesurface of a mold with unvulcanized rubber material in viscous and tackyform, so as to form a substantially closed body,

said rubber material having a vulcanizing agent intermixed therewith andthen vulcanizing the rubber by heat at a temperature which issufficiently low tocause the rubber material to remain self-adherent tosaid surface during the vulcanization.

8. A method of making a rubber article which consists in coating thesmooth surface of a mold with unvulcanized rubber material in viscousand tacky form so as to form a substantially closed body, said rubbermaterial being intermixed with a vulcanizing agent and containing arubbersolvent in sufficient proportion to make the rubber materialself-adherent to the mold surface, and then vulcanizing the rubber byheat and driving oif the residual solvent, at a temperature which issuificiently low to cause the rubber material to remain self-adherent tosaid surface and to maintain its general shape and thickness, during thevulcanization, and then separating the vulcanized rubber article fromthe mold.

9. A method of making a hollow rubber article which consists in coatingthe interior surfaces of a mold which consists of a plurality ofsections, with rubber material in moist and viscous and tacky form, andvulcanizing said rubber material while said sections are held inassembled relation, the vulcanization being conducted under heat andwith sufficient rapidity to vulcanize the rubber material while itretains its adherence to the mold sections.

10. A method of forming a hollow rubber article which consists inspreading the unvulcanized rubber in viscous and adherent form upon thesurfaces of a plurality of mold sections so that the rubber adheres tosaid mold sections, said rubber having vulcanizing material intermixedtherewith, then assembling the mold members so that the unvulcanizedrubber material has the conformation of the desired article, and thenvulcanizing the rubber by heat and with suflicient rapidity so that theadherence of the rubber maintains it in the desired shape during thevulcanization.

11. A vulcanized rubber article consisting of a plurality of sections ofvulcanized rubber which are vulcanized to each other, each said sectionhaving been formed by vulcanizing a layer of viscous rubber materialwhile said rubber material was in self -adherent form and while saidmaterial was held by its self -adherence on a form, said sections havingmerged portions.

LEVI M. ROSENTHAL.

